Re: [RFC][PATCH] Runtime switching of the idle function [take 2]

[Andi Kleen]

On Tue, Nov 29, 2005 at 03:35:39PM -0500, Lee Revell wrote:
> On Tue, 2005-11-29 at 20:53 +0100, Andi Kleen wrote:
> > We're mostly addressing it - there are problems left, but
> > overall it's looking good. The remaining problem is 
> > an education issue of users to not use RDTSC directly, 
> > but use gettimeofday/clock_gettime 
> 
> No the issue is to make gettimeofday fast enough that the people who
> currently have to use the TSC can use it.  Right now it's 1500-3000 nsec
> or so, Vojtech mentioned that he has a patch that could reduce that to

It's only that slow if the hardware can't do better.

And the kernel makes it only slow when using RDTSC directly
is unsafe - so if you use it directly thinking the kernel cheats
you for your cycles you're just shoting yourself in the own foot.

> 150-300 nsec.

If you have capable hardware it can already do much better.

-Andi
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/